Isothermal adsorption process for separation of organic nitrogen compounds from hydrocarbons



May 16, 1961 R. N. FLECK ETAL 2,984,620

ISOIHERMAL AOSORPTION PROCESS POR SEPARATION OP ORGANIC NITROGENCOMPOUNDS FROM HYDROCARBONS Filed Aug. l, 1957 United States Patent OISO'II-IERMAL ADSORPTION PROCESS FOR SEPA- RATION OF ORGANIC NITROGENCOMPOUNDS FROM HYDROCONS Raymond N. Fleck, Whittier, and Carlyle G.Wight,

Orange County, Calif., assignors to Union Oil Company of California, LosAngeles, Calif., a corporation of California p Filed Aug. 1, 1957, Ser.No. 675,754

7 Claims. (Cl. 20S-254) This invention relates to the refining ofhydrocarbons, particularly those contaminated with organic nitrogencompounds and other polar materials. Such hydrocarbons include thosewhich are produced as petroleum, as coal tar oil fractions, and shaleoils among others.

Many crude petroleum streams are produced from the ground and are foundto contain considerable quantities of organic compounds of nitrogen,sulfur, and oxygen in addition to the principal hydrocarbonconstituents. In some cases the incidence of the nitrogen compounds issufhcient that the nitrogen analysis runs as high as 1.0% by weight.California crude oils in many cases average 0.5% by weight nitrogenanalysis. Mexican and Venezuelan crudes have nitrogen analysis rangingfrom about p 0.2% to about 0.35% by weight. Extensive analysis of thesenitrogen-containing crudes indicate that much of the nitrogen occurs inthe form of amines or the so-called nitrogen bases. These includepyridine, quinoline, and the mono, di, tri, and tetra alkylatedderivatives of these materials, For example, in California kerosenedistillate the di, tri, and tetra alkylated quinolines and alkylatedpyridines are found. There is however considerable nonbasic nitrogenpresent in these materials. Coal tar oils produced in the coking ofcoal, contain extensive quantities of nitrogen bases and these areprincipally aromatic amines and heterocyclic nitrogen compounds. Shaleoil produced by the heating and retorting of shale rock, such as thatwhich is found in Colorado and else- Where, resembles waxy crude but ischaracterized particularly in that it contains such extensive quantitiesof organic nitrogen compounds that the nitrogen analysis runs as high asabout 2.5% by weight. Sulfur compounds are usually present also and thesulfur analysis may rise to 5.0% by weight. Oxygen compounds are presentto a lesser degree, but all seriously affect the performance of thecatalysts and adsorbents employed in many refining processes.

Crude petroleum, coal tar oils, and shale oils are principal orpotential sources of liquid fuels and solvents. The presence of nitrogencompounds in the fuel or solvent product imparts a very bad odor tothese materials. Their presence in the original oil very adverselyaffects hydrocarbon refining techniques by which the fuels and solventsor other materials are produced. They have, for example, well definedadverse effects on such processes as catalytic cracking, catalyticisomerization, catalytic reforming, and particularly platinum catalyzedhalide promoted reforming. The nitrogen compounds appear to be adsorbedon a cracking catalyst and selectively deactivate its active crackingcenters. The cracked gasoline yield may be reduced as much as 50%through the presence of suflicient organic nitrogen compounds to givethe feed a nitrogen analysis of about 0.3% by weight, and it is reducedby 75% when the nitrogen analysis reaches about 0.45%. Platinumcatalyzed reforming and other reforming processes in general are alsoadversely affected by presence of nitrogen compounds in the feed. In aplatinum catalyzed gasoline reforming system using Patented May 16, 1961a halide promoted catalyst, the nitrogen compounds appear to react withthe catalyst or the promoter to form ammonium halides which deposit inthe apparatus. This deactivates the catalyst and lowers the yield unlessthe halide is continuously replenished.

Because of these adverse effects, repeated attempts have been made toremove the nitrogen compounds from hydrocarbon feedstocks in refiningprocesses and from the products produced. For example, acid treatingwith dilute sulfuric acid forms water soluble salts with the basicnitrogen compounds, ie., the nitrogen bases or amines. It s otherwiseineffective With respect to the nonbasic nitrogen compounds. Catalytichydrogenation is effective to remove much of the nitrogen compounds, butin order to reduce their incidence in the hydrogenated product to alevel which does not adversely affect a platinum catalyzed reformingprocess for gasoline, hydrogenation pressures of the order of 5,000p.s.i. and higher are required.

The earlier suggested process for denitrogenation through contact withsolid granular adsorbents suffer from a disadvantage involving high heatrequirements in that the solids are generally cooled prior to theadsorbtion step, and then are heated to effect the displacement ordesorption of the material from the adsorbent. Not only does this raisethe quantity of heat necessary to maintain the process, but it alsoresults unavoidably in thermal stresses in the equipment and also in thegranular adsorbent particles.

The present invention comprises an improved process for the adsorptivedenitrogenation of hydrocarbon uid mixtures, and for the removal ofother highly polar materials which deactivate catalysts and adsorbents.A particular inorganic solid adsorbent is used in this process, which isfurther characterized by conducting both the adsorption and regenerationsteps at temperatures of the order of those used for'catalystregeneration. The operating temperature is sufliciently high to effectan efficient regeneration by oxidation and the adsorption step iseffected at substanially the same temperature. Because this' processallows adsorption at regeneration temperatures, the heat requirements ofthe process are only those necessary to supply heat losses from thesystem and to heat the feed stream to the operating temperature, andpart `of this heat however is recoverable. The heat requirement is thussubstantially less than 10% of that required in the normalnon-isothermal adsorption-regeneration processes. A treated productsubstantially free of nitrogen and other highly polar deactivatingcompounds is produced as a desirable product in itself or as apretreated material for feeding to subsequent catalytic or adsorptiveprocesses.

It is a primary object of this invention to provide an improved processfor the removal of highly polar adsorbent or catalyst deactivatingcompounds from fluid mixtures, such as hydrocarbon streams contaminatedwith organic compounds of nitrogen, sulfur, and oxygen.

It is a more specific object of this' invention to provide asubstantially isothermal process for the pretreatment of feedhydrocarbons by contacting the material with a solid contact materialhaving a specific aflinity for hydrocarbon organic compounds ofnitrogen, sulfur and oxygen, in preference to hydrocarbons of the sameboiling range and which includes a regeneration step in which thesecompounds' are burned from the solids by an oxygen-containing gas atsubstantially the adsorption temperature.

It is a more specific object of this invention to provide a pretreatedhydrocarbon stream from which harmful organic compounds of nitrogen havebeen removed by means of an isothermal regenerative solid adsorptionprocess employing a metallo alumino silicate absorbent havingsubstantially uniform sized pores of greater than about 7 A. in diameterand which operates at a temperature on the order of 700 `F. to aboutl050 F.

' It is another object of thisrinv'ention to effect the denitrogenationof yhydrocarbon -mixtures contaminated with organic compounds ofnitrogen by means of an isothermal adsorption-regeneration processwherein the solid adsorbent is a static or moving bed, or may beuidized.

Other objects and advantages of the present invention will become moreapparent to those skilled in the art as the descriptionand illustrationthereof proceed.

Briefly, the present invention comprises an 'improved process fortreating hydrocarbon streams contaminated with highly polar compoundswhich are known to deactivate adsorbents and catalysts, Vsuch as organicnitrogen, sulfur, and oxygen compounds derived from virtually anysource, to remove such compounds and produce a noncontaminatedhydrocarbon stream. The subsequent description will involve removal ofnitrogen compounds :for the sake of simplicity, and Vwith theunderstanding that the oxygen and sulfur compounds are also removed.

In general, the process consists in contacting the hydrocarbon feedcontaminated with organic nitrogen compounds with a granular solidnatural or synthetic metallo alimino -silicate zeolite of the typegenerally referred to as molecular sieves organic. The organic nitrogencompounds are actively separated from the hydrocarbons by sorptionmechanisms and it is possible to produce in one or more contactingstages a virtually nitrogen-free hydrocarbon product, that is, onehaving a zero nitrogen analysis. The solid contact material saturatedWith the nitrogen compounds is then regenerated by air oxidation wherebythe nitrogen compounds are burned of, leaving the metallo aluminosilicate free of these materials and in condition to treat additionalfeed. The regenerated material is then reemployed to contact furtherquantities of the contaminated feedstock.

It has now been found that both of these adsorption and regenerationsteps may be effected satisfactorily at temperatures which are equal tothe regeneration temperature, so that the entire process becomes anisothermal operation. The oxygen-containing gas is fed into theregeneration zone in contact with the rich adsorbent and the nitrogencompounds are burned from the adsorbent at temperatures in the range offrom about 700 F. to about 1050" F., depending upon the speed desired toeffect the regeneration, the quantity and nature of the nitrogencompounds present on the adsorbent, the thermal stability of theadsorbent and the feedstock, and such considerations. Temperatures belowabout 700 F. are not satisfactory because the oxidative regenerationcannot be initiated or maintained, and temperatures 'above about l050 F.are not'satisfactory because the adsorbent is destroyed.

Surprisingly these specific Vadsorbents are able to absorb practicallyquantitatively the basic and non-basic nitrogen compounds from thesehydrocarbon streams at substantially these same temperatures. Theparticular adsorbents involved are hereinafter more particularlydescribed.

For example, a gasoline stream which is to be fed to a platinumcatalyzed reforming process may contain organic nitrogen compounds tothe extent that thefeed analyzes about 0.1% by weight. Some organiccompounds of sulfur and oxygen are also usually present. The process ofthis invention, operating essentially isothermally at temperatures ofthe order of from 700 F. to 1050" F., can effectively reduce thenitrogen analysis of the effluent to values on the order of one part permillion as shown in the following examples. It is not necessary howeverthat the effluent be subjected to further treatment since there are manycases in which hydrocarbon mixtures are desirable in and of themselvesafter the substantially complete denitrogenation has been effected. Theeffluent, from the process of this invention, under proper solids uidratio control, is `free of organic nitrogen compounds and the otherpolar compounds in general and is thus in especially excellent conditionfor subsequent treatment in the noble metal catalyst refining processessuch as reforming.

It has also been found that the nitrogen content of the emuent producedin the process of this invention is af fected by the rate at which thefeed stream is passed through contact with the adsorbent. This effect iscritical insofar as it determines the maximum rate at which a given bodyof adsorbent can effectively reduce the nitrogen analysis of aparticular type of hydrocarbon feed. In general however for theparticular zeolitic silicate adsorbents referred to, the extent to whicha given quantity of adsorbent may treat a given feed to produce aneffluent analyzing less than about l0 ppm. of nitrogen is limited by thenitrogen compound concentration on the adsorbent, specifically about0.2% by weight absorbent nitrogen analysis with a moving absorbent bed,and somewhat less with a static bed. At values above this the adsorbentis apparently saturated with nitrogen compounds and break-through ofthese materials occurs. However, even exceeding this value, the effluenthas a substantially reduced nitrogen analysis compared with the feedstream but the extent of the denitrogenation is somewhat -less and theproduct will have a somewhat higher nitrogen analysis-than the 10 p.p.m.value mentioned above.

The solid contact material employed in the process of this invention isa solid granular material having a mesh size range between about 2 and300 mesh or smaller, preferably between about 4 and about 30 mesh forstatic or moving solids bed Contact, and preferably between about 30 and200 mesh for lluidized contacts. It may be used in the form of a densecompact bed of material through which the nitrogen compound containingstreams pass, either in the vapor phase or in the liquid phase. Theprocess may employ a single static bed of material in which case theprocess is only semicontinuous. Preferably a plurality of two or morestatic beds of solids are employed with appropriate remotely operablevalving so that the streams pass through one or more of the contactingvessels in a set while the regeneration stream passes through one ormore of the other vessels in the set. In this case the feed and productflows are continuous, in either the vapor or liquid phase, and either upor down through the solids.

Another modification employs a continuously moving solids bed. In thiscasethe ilow of feed is maintained continuously through one or morecontacting zones. The flow of regeneration fluid is maintainedcontinuously through a second contacting zone, and the granular solidsare recirculated successively through these Zones.

In another modification using the smaller sized mesh ranges or powderedsolids, the material may be suspended or lluidized in and by the fluidstreams contacting it, and a single or several stages are employed.

A number of theoretical and actual contact stages greater than one isreadily obtained in moving bed systems using a single contacting zone,or with several static beds, or with several iluidized contacting zones.Plural stage contacting is highly desirable in the production of anefuent of very low nitrogen analysis, that is, of the order of about 1ppm. (parts per million) and below'. Reduced solids to oil ratios alsoresult. A single contact stage is frequently sufficient, even withfeed-stock of high nitrogen analysis, where the product nitrogenanalysis need only be reduced to about 0.1% by weight.

The present invention may not be carried out with the commonly availablesolid granular adsorbcnts such as alumina, silica gel, charcoal, etc.,primarily because at temperatures of the order of 700 F. to l050 F. theylose their adsorption capacity for organic compounds of nitrogen,sulfur, and oxygen. It has been changes the pore diameter.

found that particular materials which are highly eicient and preferredin the hydrocarbon denitrogenation process of the present invention arethe natural or synthetic crystalline zeolitic metallo alumino silicatesactivated by partial dehydration and having pores in their crystalstructure which are 7 A. or more in diameter. The composition of onetypical synthetic zeolite having a pore size of about 13 A. is5Na2O.6Al2O3.15SiO2. It may be prepared by heating stoichiometricquantities of alumina and silica and excess caustic under pressure. Theexcess caustic is washed out. Other desired metal ions, such as calcium,for example, may then be introduced by ion exchange. Part of the sodiumin this material can be ion exchanged with concentrated salt solutionsat superatmospheric pressure and temperatures of 150-300" C. tointroduce other metal ions. Another adsorbent having pore diameters ofabout A. is 5CaO.12Al2O3.30SiO2. The particular added metal ion Certainnaturally occurring minerals, such as chabazite, analcite, gmelinite,and the like can be heated to dehydrate the molecule partially andobtain an activated zeolitic material similar in denitrogenationproperties to the manufactured materials. These natural and syntheticmaterials are all zeolites and their sodium and calcium derivatives arevery stable solids which apparently have pores active for hightemperature adsorption and which are quite uniform in size. Otherderivatives have different sized pores The metallo alumino silicateshaving pore diameters of 7 A.

`or more exert strong adsorptve effects on the polar hydrocarboncompounds of nitrogen, sulfur, and oxygen, whereas the hydrocarbons ofthe same boiling range are substantially unaffected.

The synthetic crystalline metallo alumino silicate zeolites having porediameters of 7 A. or larger are presently available items of commercemarketed by Linde Air Products Company, 30 E. 42nd Street, New York 17,New York, under the name of Molecular Sieves 10X, 13X, etc., and thesehave pore diameters averaging 10 A. and 13 A. respectively.

The process of the present invention and several of its modificationswill be more readily understood by reference to the accompanyingdrawings in which:

Figure l is a schematic flow diagram and an elevation View of part ofthe apparatus used to effect the process lof this invention with amoving bed of the granular adsorbent,

Figure 2 is a simplified schematic flow dlagram of the `process of thisinvention using uidized solids techniques well known to those skilled inthe art, and

Figure 3 is a simplified schematic flow diagram illustrating the staticsolids bed modification of this process.

Referring now more particularly to Figure 1, the essential apparatuselernents involved include feed pump 10, feed heater 12, and contactcolumn 14 containing regeneration zone 16 and adsorption zone 18. Incontacting column 14 the metallo alumino silicate adsorbent isrecirculated downwardly as a moving bed successively `throughregeneration gas disengaging zone 20, regeneration zone 16, regenerationgas engaging zone 22, sealing zones 24 and 26 on opposite sides of sealgas engaging zone 23, effluent disengaging zone 30, adsorption zone 18,feed engaging zone 32, a sealing zone 34, second'seal gas engaging zone36, and solids feeder zone 38 within which the rate of flow of themoving bed of solid adsorbent and the uniformity of flow throughout thecolumn cross section are determined. Any sort of a solids elevator 40such as mechanical, pneumatic, or other, is provided to recirculateadsorbent removed from lthe `bottom of column 14 to the top of thatcolumn.

Column 14 is of course provided with external insulation not shown toreduce heat losses of the system to an absolute minimum.

The feed stream, for t present purposes of illustration, is consideredto be a naphthenic gasoline suitable as a catalytic reformer feed andwhich analyzes about 0.1% by weight of nitrogen. These nitrogencompounds include the basic nitrogen bases such as pyridine, alkylatedpyridines, quinoline, alkylated quinolines, and the like and othernonbasic nitrogen compounds such as pyrrole, alkylated pyrrole,nitriles, diphenylamine, etc. This feed stream is introduced throughline 42 and is pumped by means of pump 10 through line 44 at a ratecontrolled by valve 46 through heat exchanger 48 in which, if thetreated efuent is not sent to a subsequent treating step in which itshould be at an elevated temperature, the feed is preheated by exchangewith the efliuent removed from disengaging zone 30 through line 50. Thefeed, thus possibly partially preheated, is introduced through line 52into a tired feed heater and vaporizer 12. Fuel is introduced into thispreheater through line 54 ata rate controlled by valve 56 in accordancewith temperature recorder controller 58 at thermocouple point 60disposed at some appropriate location within adsorption zone 18. Thefeed vapor continues through transfer line 62 and is introduced intofeed engaging zone 32. The vapor passes upwardly countercurrent to thedownwardly moving adsorbent at a temperature which may range from as lowas about 700 F. to as high as about 1050" F. The feed rate is controlledat a value relative to the rate of tlow of the adsorbent so as toproduce an efiiuent having a nitrogen analysis which is suitable for theparticular purposes at hand. If this is to be a catalytic reformer feedthe nitrogen content is preferably as low as about one part per million.Under these circumstances the rate of hydrocarbon feed flow throughadsorption zone 18 is preferably kept below a rate which is equivalentto adsorption of not more than about 0.2% by weight of nitrogen on theadsorbent. This of course can be readily controlled by adjustment of theadsorbent to feed ratios in zone 18.

The nitrogen compounds, both basic and nonbasic, and any other polarcompounds which may be present in the feed stream, are adsorbed by theadsorbent at the elevated temperature and are retained thereby while thehydrocarbon components remain substantially unadsorbed and collect ineffluent disengaging zone 30. If this material is to be used per se itis removed through line 50 at a rate controlled by valve 64 and passesthrough line 50 and exchanger 48 and continues through line 66 andproduct aftercooler 68. This material is sent to storage facilities orother operations not indicated. Typically however, the thus treatedhydrocarbon stream comprises the feedstock to a catalytic reformingoperation in which case it is removed from effluent disengaging zone 3i)through line 70 at a rate controlled by valve 72. fIt is in the vaporphase under the circumstances and conditions selected for purposes ofthis example and may be heated additionally if necessary to reformingtemperatures and then introduced into the catalytic reforming zone notshown. In some cases it may be necessary to cool the adsorption zoneeffluent slightly if the reforming temperature desired is somewhat lessthan the adsorptiontemperature maintained in adsorption zone 1S.

The spent adsorbent passes downwardly through sealing zone 34, a sealinggas is introduced into second sealing zone 36 by means of line 74 at arate controlled by valve 76. This sealing gas may be steam, oxygen-freeflue gas, carbon dioxide, methane, hydrogen, nitrogen, or any otherinert fluid which is compatible with the adsorbent employed, with thehydrocarbon feed stream treated, and any subsequent operations on theeifluent.

The adsorbent continues downwardly through solids feeder zone 38 at atemperature still ranging between 700 Rand 1050 F. and is conveyedthrough conveyor 40V to the top of column 14. The hot rich adsorbentpasses downwardly as a moving bed through regeneration zone 16 throughwhich is maintained a recirculating stream of regeneration gas, which inthis case is a stream of flue gas or combustion gas produced in thisregeneration and to which a small but etective amount of oxygen or airis introduced in quantities suicient to maintain the combustion. Anoxygen-containing gas such as air Yor any other such gas, is introducedby means of blower Y'i8 and lines 30 and 82 at a rate controlled byvalve 84 and temperature recorder controller 86 which in turn isactuated by temperature control point 8S. This air is mixed with spentue gas flowing through line 90 from cooler V92 forming a gas mixtureconsisting essentially of nitrogen, carbon dioxide and water vapor, butwhich also contains a small controlled quantity of oxygen which mayrange between about 0.1% and about by volume. This fresh regenerationgas is forced through regeneration zone 16 by means of blower 94 at arate controlled by valve 96. This gas passes upwardly throughregeneration zone 16 and effects the combustion of the adsorbed nitrogenand any other adsorbed polar compounds on the adsorbent. This is anexothermic reaction and heat is liberated in this step to the extentthat the combustible material is adsorbed on the adsorbent. Hot flue gasis disengaged from zone and is passed through line 9'8 to stack 100 at arate controlled by valve 102. Part of the ue gas however is recirculatedthrough cooler 92 in which part of the heat of regeneration isdissipated. This produces the recirculated fraction of regeneration gasto which the oxygen is added to produce the fresh regeneration uid.

To elect startup of the process of this invention natural gas or otherfuel may be introduced through line 104 at a rate controlled by valve106 and burned with air introduced as previously described intoregeneration zone 16. After the entire circulating mass of adsorbent hasbeen raised to the desired operating temperature within the limits setpreviously, the feed stream flow is started at approximately the sametemperature in the manner also previously described. As the combustilenitrogen and other polar compounds accumulate on the adsorbent,combustion of these materials begins in regeneration Zone 16 and iseffective to supply at least part and sometimes all of the heatnecessary to maintain the process. In this case the opening of valve 106is gradually reduced until a setting is reached to maintain theregeneration temperature at approximately the desired value. This mayresult particularly when relative small amounts only o f adsorbedmaterials are available for burning.

With feed streams containing rather extensive quantities of organiccompounds of nitrogen, e.g., in some shale oil fractions in which thenitrogen analysis may rise as high as 2.0% by Weight, there is asufficient amount of adsorbed nitrogen compounds and the like which whenburned will maintain the desired operating temperature of the solids inregeneration Vzone 16 and even generate an excess of heat which must bedissipated in cooler 92. If the desired operating temperature issomewhat lower than the maximum allowable limit set vby the adsorbent,then the temperature of the adsorbent during regeneration may be allowedto rise to a value of about l050 F. for example and the heat dissipatedby direct heat exchange in the adsorption zone with a feed stream whichis introduced at a temperature somewhat below the desired operatingtemperature. For example the feed may be introduced at 600 F., be heatedin adsorption zone 18 through adsorption of the sensible heat of theregenerated adsorbent to the desired operating temperature of 800 F. forexample, and then removed at about this temperature. The spent adsorbentunder these conditions is removed from adsorption zone 1S and introducedinto regeneration zone 16 at a temperature of about 600 F. for example.The combustion of a large quantity of organic nitrogen compounds willraise this temperature to the maximum value before stated. ln this wayheat exchange required in the proc- -ess is all or largely effectedinside column 14. The temperature change between 600 F. and 1050 F.causes 8 some thermal stress in the system and in the solids, but it isvery substantially less than the thermal stress characteristic ofadsorption processes in which the feed stream is treated in anadsorption zone at a temperature of the order of 70 F. to 100 F., andthen is regenerated under combustion conditions at temperatures on theorder of 900-l000 F. or higher.

lt should be understood that the description of Figure l is merelyillustrative and that modifications may be made therein within thecontemplation of this invention. For example, the position of theadsorption and the regeneration zones may be reversed from that shown ifdesired. The seal streams employed may be modified if desired byremoving a mixture of the gases present in Ythe contacting columninstead of injecting a seal gas which turns up in the product streams asa contaminant. The use of other solids-fluid contacting process steps inconjunction with the process of this invention is contemplated, butsince many of these are Well known in the art they will not beextensively discussed here.

Although the previous example has dealt with gaseous fluids and sinceunder the relatively high operating temperatures of 700 F. to 1050 F.most hydrocarbons are in the vapor phase, it is not intended to limitthe present invention to vapor phase contacting only. ltV is well knownfor example that some hydrocarbon fractions remain in the liquid phaseat temperatures above about 700 F. and do not begin to decomposethermally or otherwise until temperatures of the order of 900 F. arereached. With such materials the process of the present invention may beeffected with the feed stream contacting the adsorbent in the adsorptionzone in the liquid phase. Obviously there are conditions of feed streamsof relatively wide boiling range in which the feed stream may be in amixed condition, that is, partly vapor and partly liquid.

Referring now more particularly to Figure 2, a very simple schematicflow diagram of the process of the present invention, utilizing uidizedsolid techniques well known to those skilled in the art, is shown. Hereadsorption zone and regeneration zone 112 are shown. 'Ihe feed stream isintroduced through line 114 controlled by valve 116 and passes upwardlythrough transfer line 118 into adsorption 'zone 110. Hot regeneratedsolid adsorbent is dropped through standpipe 120 provided with valve 122to form a iluidized suspension of solids. This suspension passesupwardly to adsorption zone 1110 and forms fluidized solids level 124.The unadsorbed hydrocarbons are discharged through line 126, the spentadsorbent is discharged through standpipe 128 controlled by valve 130.

The spent adsorbent is dropped into a stream of oxygen-containingregeneration gas iiowing through line 132 at a rate controlled by valve134 and it passes upwardly into regeneration zone 112 through transferline 136. Fluidized solids level 138 is maintained herein and adsorbedcompounds combustion takes place. Hot stack gases are dischargedvthrough line 140 and the regenerated hot solids are dropped throughstandpipe 120 into transfer line 118 to contact further quantities ofthe feed.

It is contemplated that the various heat exchange and flow control stepsshown in Figure l would also be used in the process of Figure 2, andthat further techniques characteristic of fluidized solids processeswould also be employed. These are well known to those skilled in theart.

In Figure 3 is shown a simplified schematic drawing of a continuousprocess employing static or stationary beds of solid adsorbent. A pairof vessels and 152 are provided containing a static bed of theparticular solid granular adsorbent disclosed previously. The ow offluid through these vessels is staggered so that at any given time atleast one bed of adsorbent is contacting the feed stream while theVother is being regenerated according to the `process of this invention.XIn Figure 3 the feed stream is introduced through line 154 and four-waycontrol valve 156 and passes upwardly through adsorber 150, from whichthe unadsorbed fraction is removed through line 158 and four-way controlvalve 160. Simultaneously an oxygen-containing regeneration gas flowsthrough line 162 and valve 160 downwardly through adsorber 152 in whichthe adsorbed materials are burned from the adsorbent. The efduent stackgases are discharged through line 164 and tlow through fourway controlvalve 156 to the stack. The intermittent actuation of control valve 156and 160 is controlled by cycle timer operator instrument 166 in asuitable sequence. Again the various temperature and ow control stepsequivalent to those described in Figure 1 are to be employed in thismodification of the process to effect substantially isothermaladsorption and oxidative regeneration steps on the adsorbent.

In one application of the process of this invention a relatively heavyhydrocarbon mixture was processed with a moving bed of the adsorbentaccording to the present invention. The metallo alumino silicateadsorbent had pore diameters of about 13 A. and was maintained at atemperature of 900 F. The operating pressure was substantiallyatmospheric. The feed stream was a highly aromatic catalytic cycle oilfrom a catalytic cracking operation and had a boiling range of about450-650 F. The oil was in the vapor phase during the process. Itanalyzed 0.096 Weight percent nitrogen Kjeldahl. The regenerationtemperature was held at 900 F. by variation of the quantity of oxygencontained in a flue gas introduced during the regeneration step. rIhefeed to adsorbent ratio in the adsorption zone was controlled so thatthe spent adsorbent analyzed about 0.13% by weight nitrogen. This issuiciently below the maximum nitrogen concentration discussed above andaccordingly the nitrogen analysis of the effluent obtained was about0.003% nitrogen by weight.

A repeat operation duplicating the conditions given immediately abovewas carried out with the single exception that the feed to adsorbentratio was reduced to produce a spent adsorbent analyzing only about0.08% by weight nitrogen. Under these circumstances the etlluentanalyzed 0.001 weight percent nitrogen Kjeldahl. This corresponds to anefuent analyzing p.p.m. of nitrogen.

The same operation was repeated with the same feedstock except that theregeneration and the adsorption temperatures were reduced to a Value asclose to the minimum at which combustion could be initiated andmaintained, that is, a temperature of about 70l0 F. The feed toadsorbent ratio was substantially reduced to produce a spent adsorbentanalyzing about 0.08% nitrogen by weight. This is also substantiallybelow the maximum ligure previously discussed and the efuent analysisvaried slightly near 0.0001 weight percent nitrogen Kjeldahl. This is 1p.p.m. of nitrogen compound contamination and for most purposes theeluent is clean.

The 10 A. zeolitic silicate adsorbent referred to above givessubstantially identical degrees of nitrogen compound adsorption.

The process of the present invention is readily applicable to thepretreatment of the hydrocarbons in the gasoline boiling range. Theremoval of organic compounds of nitrogen in such instances is extremelyimportant for several reasons. First, such compounds impart to gasolinean extremely disagreeable odor. Second, the presence of even very smallconcentrations of such nitrogen compounds has an extremely adverseeffect upon the performance of certain halide-promoted platinumcatalyzed dehydroarornatization processes employed in the refining ofgasoline to raise the antiknock rating thereof. The nitrogen compoundsappear to react either with the halide promoter or the catalyst in somemanner with the formation of extensive quantities of ammonium halidesalts which precipitate in the system and cause plugging problems.Third, and in addition to the plugging problems, the ammonium halideformation, if

allowed to continue, also simultaneously tends to deactivate thecatalyst through removal of the promoter and ultimately results indecreased yields and octane improvement. The other polar sulfur andoxygen containing contaminants have well known undesirable effects.

In all of the preceding discussion, the nitrogen analyses given orreferred to are Kjeldahl total nitrogen determinations and express theconcentration of organic cornpounds of nitrogen, either in the fluid oron the adsorbent, as weight percent nitrogen.

It has been found that the process of this invention may be conducted inthe liquid phase with heavy or high boiling feedstocks at contactingtemperatures on the order of those noted above to effect a substantialdegree of denitrogenation. It has been found also that at highertemperatures in this range the rate of denitrogenation is considerablyhigher as indicated by the lower nitrogen analyses of the products.

With lighter feedstocks it is preferred to treat them in the vapor phasebecause the holdup on the solids of feed hydrocarbon is considerablyreduced and the denitrogenation rate is higher. With heavier feedstocksit is possible to treat them in the vapor phase by contacting them atreduced pressures with the silicate solids. lt is also possible to sotreat them by employing diluent gases such as hydrogen, nitrogen, carbonmonoxide, carbon dioxide, methane, and other well known light and inertgases. With the very heavy feedstocks the contact must of necessity beconducted in the liquid phase as these materials are frequentlynon-vaporizable. Their contacting is facilitated under thesecircumstances with the use of diluent solvents.

A particular embodiment of the present invention has been hereinabovedescribed in considerable detail by way of illustration. It should beunderstood that various other modifications and adaptations thereof maybe made by those skilled in this particular art without departing fromthe spirit and scope of this invention as set forth in the appendedclaims.

We claim:

1. The process for the denitrogenation of a hydrocarbon mixturecontaminated with organic nitrogen cornpounds, including heterocyclicnitrogen bases, having boiling points within the boiling range of thehydrocarbon components of said mixture, in minor amounts but not in suchquantities that said mixture analyzes more than yabout 2.5 percent byweight of nitrogen, which process comprises: (l) contacting said mixturewith a lean solid partially dehydrated zeolitic metallo alumino silicateadsorbent having substantially uniform pores of between about 7 A. andabout 13 A. in diameter, whereby there is obtained a non-adsorbedhydrocarbon phase and a rich adsorbent containing said organic nitrogencompounds; (2) separating said non-adsorbed phase from said richabsorbent; and (3) contacting said rich adsorbent with anoxygen-containing gas for a period of time sufficient to burn off saidorganic nitrogen compounds and return the adsorbent to its lean state;said steps (1), (2) and (3) being carried out at substantially the sametemperature between about 700 F. and about 2. A process according toclaim l wherein said zeolitic adsorbent has a composition correspondingsubstantially to 5Na2O.6Al2O3.15SiO2 and has pores of about 13 A. indiameter.

3. A process according to claim l wherein said zeolitic adsorbent has acomposition corresponding substantially to 5CaO.l2Al2O3.30SiO2 and haspores of about l0 A. in diameter.

4. A process as defined by claim l wherein said step (l) is terminatedto be followed by said step (2) when the total nitrogen content of saidrich adsorbent reaches a value not greater than about 0.2 percent byweight.

5. A process for the denitrogenation of a petroleum hydrocarbon mixturecontaminated with normally incident organic nitrogen compounds,including heterocyclic nitrogen bases, having boiling points within theboil range of the hydrocarbon components of said mixture, in minoramounts` but not in such quantities that said mixture analyzes more thanabout 2.5 percent by weight of nitrogen, which process comprises (1)passing said mixture at a temperature between about 700 F. and about1050 F. through a bed of a lean solid partially dehydrated zeoliticmetallo alumino silicate adsorbent having substantially uniform pores ofbetween about 7 A. and about 13 A. in diameter, whereby there isobtained a non-adsorbed hydrocarbon phase of reduced nitrogen contentand a. rich adsorbent containing adsorbed organic nitrogen compounds;(2) separating said non-adsorbed hydrocarbon phase from said richadsorbent at a temperature within said range; (3) passing anoxygen-containing gas through said rich adsorbent at a temperaturewithin'said range and for a period of time sufficient to burn off saidadsorbed organic nitrogen compounds and return the said adsorbent to itslean state; and (4) returning the lean adsorbent so obtained to step(1).

6. A process according to claim 5 wherein, in step (1),

12 said adsorbent is moved through an adsorption zone wherein itcontacts said hydro-carbon mixture countercurrently, and, in step (3)said rich adsorbent is moved through a regeneration zone wherein itcontacts said oxygen-containing gas.

7, A process according to claim 6 wherein the flow rates ofsaidhydrocarbon mixture and said adsorbent through said adsorption zone areso controlled relative to each other that the rich adsorbent withdrawnfrom said adsorption zone contains not more than about 0.2 percent byweight of nitrogen.

References Cited in the le of this patent UNITED STATES PATENTS2,413,134 Barrer Dec. 4, 1946 2,834,429 Kinsella et al. May 13, 19582,859,256 Hess et al. Nov. 4, 1958 OTHER REFERENCES Article by Barrer,Journal of the Society of the Chemical Industry, vol. 64, May 1945(pages 130-135).

1. THE PROCESS FOR THE DENITROGENATION OF A HYDROCARBON MIXTURECONTAMINATED WITH ORGANIC NITROGEN COMPOUNDS, INCLUDING HETEROCYCLICNITROGEN BASES, HAVING BOILING POINTS WITHIN THE BOILING RANGE OF THEHYDROCARBON COMPONENTS OF SAID MIXTURE, IN MINOR AMOUNTS BUT NOT IN SUCHQUANTITIES THAT SAID MIXTURE ANALYZES MORE THAN ABOUT 2.5 PERCENT BYWEIGHT OF NITROGEN, WHICH PROCESS COMPRISES: (1) CONTACTING SAID MIXTUREWITH A LEAN SOLID PARTIALLY DEHYDRATED ZEOLITIC METALLO ALUMINO SILICATEADSORBENT HAVING SUBSTANTIALLY UNIFORM PORES OF BETWEEN ABOUT 7 A. ANDABOUT 13 A. IN DIAMETER, WHEREBY THERE IS OBTAINED A NON-ADSORBEDHYDROCARBON PHASE AND A RICH ADSORBENT CONTAINING SAID ORGANIC NITROGENCOMPOUNDS, (2) SEPARATING SAID NON-ADSORBED PHASE FROM